The invention relates to an apparatus for measuring the pressure of fluids, particularly liquids. More specifically, the invention is directed to a transducer apparatus for measuring the pressure of a moving fluid stream.
There are many industrial operations which require continuous monitoring of the pressure generated by a moving fluid stream. One example is an operation referred to in the petroleum industry as hydraulic fracturing. In a typical fracturing operation, viscous liquids or slurry compositions are pumped into the well bore, by positive displacement pumps, at high pressures and high velocities. From the well bore, the pressurized liquid pushes into the rock formation containing the oil or gas to be recovered and "fractures" the rock outwardly from the well bore. The resulting cracks in the formation enhance the flow of the oil or gas into the well bore.
One way to measure the pressure of the fracturing fluid being pumped into the well bore is to install a pressure measuring device in the pipeline which carries the fluid from the pump to the well head. This places the pressure measuring device down stream from the high pressure side of the pump, so that it can measure the "average" line pressure. The type of devices usually employed for this purpose are conventional transducer instruments, which include resistance strain gauges or piezo beam strain gauges as the sensor components.
These instruments have several drawbacks which make them impractical for measuring the pressure of a moving liquid in the harsh environment of a field operation, such as that described above. For example, such instruments are highly sensitive to slight movements and to extreme temperature conditions. Because of the sensitivity factor, the signal output of the transducer must be electrically conditioned to get a gauge reading which is representative of the actual pressure of the fluid being monitored. Since these instruments are sensitive to movement, they are extremely vulnerable to vibration and shock, and they usually fail completely in situations where the fluid makes two or three consecutive pressure surges through the line which carries the fluid from the pump to the well head, or some other use point.
The transducer apparatus of this invention has a distinct advantage over the prior devices. For example, it is not sensitive to slight movements, it is not affected by wide variations in temperatures, and it is capable of responding rapidly and accurately to pressure surges ranging from zero pressure to very high pressures, without damaging the instrument or otherwise affecting its integrity.